"USB 3.0 might be one of the big stories here at IDF, but Intel just showed off a glimpse of the future: Light Peak, an optical interconnect for mobile devices that can run as fast as 10Gbps. That's fast enough to do everything from storage to displays to networking, and it can maintain those speeds over 100-meter runs, which is pretty astounding. Intel says the idea is to drastically reduce the number of connectors on mobile devices, which should allow them to get even smaller - but the demo was on a huge Frankenrig, so don't expect to see Light Peak devices shipping any time soon."

Simple, Ethernet requires fiber or CAT5/5E/6 cables which are usually far thicker than your average keyboard/mouse cable, plus, the price of the MAC/PHY will most likely increase the price of low-end peripherals that don't really require 10Gbps bandwidth. (Mouse/keyboard/webcam/printer).
... Though Intel might be using Ethernet as their carrier protocol. (The 10GbE figure looks suspicious)

Having said all that, I do agree that Ethernet (as a carrier protocol) can be used to replace a -lot- of proprietary protocols (USB anyone?) - heck, it can even be used to talk to high bandwidth expansion cards. (Yes PCI-E/MSI-X, I'm looking at you.)

As for Infiniband, game over people.
In less than two years, the price of a -fiber- SR 10GbE NICs went down from >5K$/port to less than 800$/port.
Unless something changes, you'll be able to buy a UTP-capable 10GbE NIC for 100$ and pay 1$ for each 3ft of CAT7 cable in 3-4 years...
Sure, Infiniband 12x will most likely beat 100GbE to the punch, but you simply cannot beat the economy of scale.

Exactly - use ethernet as the base protocol (with the usual layering on top) and you can run it over whatever physical medium you like - at most you then only need a media converter (as opposed to needing something smarter like trying to run say Parallel over USB). Existing media standards could of course be reused for certain applications.